Technical Abstract:
Fusarium wilt (FW) is a major disease of watermelon in North America and around the world. Control of this disease is difficult because the soil-borne causal agent Fusarium oxysporum f. sp. niveum (Fon) produces chlamydospores that remain infectious in the soil for many years. Although, various levels of resistance to Fon races 0 and 1 exist in watermelon cultivars, no resistance to race 2 or 3 has been reported. We have identified three Citrullus lanatus var. citroides plant introductions from the U.S. germplasm collection with high levels of resistance to Fon race 2. The most resistant individuals of each of these PI have been self-pollinated three times, with resistance screening and selection with each successive selfing. These improved lines USVL246-FR2, USVL252-FR2 and USVL335-FR2 have been extensively tested in greenhouse and field evaluations. The three lines have been found to be uniform, and exhibit a resistance phenotype significantly higher than that found in the watermelon cultivars Sugar Baby, Charleston Grey and Calhoun Grey, and have levels of resistance equal to or higher than the reported resistant lines, PI296341, PI271769, and 296341-FR. Data from greenhouse and field trials will be presented.